Fertility Assessment by Continuous Breeding: Evaluation of Diethylstilbestrol and a Comparison of Results from Two Laboratories

Diethylstilbestrol (DES) was selected as a positive control compound to study a new assay for reproductive toxicity testing. The assay, Fertility Assessment by Continuous Breeding, has been used at 2 different testing laboratories. This manuscript describes the results of 1 study and compares the reproducibility of the data from the 2 laboratories. CD-1 mice re-ceived a diet with DES at concentrations of 0, 1, 10, and 50 ppb (pg/kg) throughout the study. The treatment began 7 days before cohabitation, and then, for a 14-week period, the mice were housed as breeding pairs, and litters were weighed, sexed, and discarded to allow continuous matings. The males and females were separated at the end of 14 weeks, and the last litter was saved until weaning. The control pairs delivered an average of 4.75 litters per fertile pair, and 95 % of the pairs had at least 1 litter. DES in feed at 50 ppb de-creased fertility so that only 42 % of the pairs were fertile, and the number of litters per fertile pair averaged only 1.38. Litter size and offspring survival were adversely affected by DES (50 ppb) in the diet. Data from the 2 laboratories performing these tests were simi-lar, indicating that the studies were highly reproducible